Electrically wound clock



Feb. 1, 1944. v. J. s. RUSSELL ET AL 2,340,697

ELECTRIGALLY WOUND CLOCK Filed Aug. 28, 1942 Patented Feb. 1, 1944 ELEGTRICALLY WOUND CLOCK Victor James Samuel Russell and'Eric Beecroft Moss, Cricklewood, England, uassignors =t S. Smith. ;& -,Sons (Motor Accessories). Limited, -Cricklewood, London,- England, azBritish com- Application August 28, 1942, Serial No.'456,552

In Great Britain J une 30,1941

Claims.

This invention relates to electricallywound clocks of the-kind'in which the clockwork mechanism as it runsdown'closes a switch and completes an electric circuit to energise an electromagnet, which magnet operates an armature arranged to re-stress the winding spring and to interrupt the electric circuit. In such clocks,-where the armature moves with the unwindin of the clock the circuit is usually completed by a snapaction switch, which is closed by the armature at one limit of its movement. This type of switch has been employed because the switch requires tobemaintained in its closed position during the movement-of the armature under the control of the electromagnet, since the armature then ceases to apply a-closing' force to the switch.

According tothe present invention an electrically woundclock-of the kind first referred to above is-characterised in 'that'a switch for controlling-the energisation of the electromagnet isbiased towards an openpositionand after being closed by means operated by the running down of the clockwork mechanism and thereby energising the electromagnet, is maintained closed by flux from the electromagnet during the resulting movement of the armature, which re-stresses the winding spring. For example, a moving part of the switch may have associated therewith asecond armature arranged in 'the'flux path of the magnet so that when the magnet is energised the second armature is'moved in opposition to the aforesaid bias.

In one form of construction according to this invention two switches are arranged in series in the electromagnet-circuit, which are respectively arranged to be operated by the first said armature at opposite ends of its movement, one of which switches. is biased towardsthe open position and is provided withsaid second armature, and the other of which is biased towards a closed position, the latter-being arranged to be opened when the armaturehas completed-its movement under the influence of the magnet, while the other switch is arranged to be 1 closed when the armature is in a position corresponding to the run-downcondition of the clock.

'Each of said switches may be of the kind comprising a pair of contacts at leastlone of which is mounted on a resilient or pivoted arm.

The movement of the'first said switch into the closed position may be by a mechanical connection between the armature or part moving therewith. Inorder to. prevent'the electromagnet winding from being overheated orrburnt out in the event of the contacts remaining permanentiy" closed, a thermostat device is arranged to beinfluenced'by-heat generated in the'electric circuit, and is arranged to open one or the other of the switches when excessive heat is generated. For example, the thermostatic device may comprise a bi-metallic strip which constitutes aflexible support for Oneof the contacts, and is encircled b a heating coil in circuit with the electromagnet.

The following is a description of two alternative forms of construction,-reierence being made to the accompanying drawing in'which both Figures land 2 are perspective views of the mechanism.

; In the construction shown in Figure 1, the-usual form of rotary armature I0 is pivoted about the mid point of theelectromagnet coil H and is provided with curved end pieces 12 which are arranged to sweep over the ends of the core iii of the electromagnet. The electromagnet circuit has two pairs of contacts I4, [5 and 16, ll respectively, arranged in series, the first said pair being biased'to open and the other being biased to close. The moving contact arm I8 which carries the contact M of the biased open pair or contacts comprises a resilient blade which is anchored at one end to an insulating block 20 mounted on a fixed part of the device. The arm has secured to its-other end a small block of magnetic material l9 which is disposed atone end of the coil in the flux path between one of the poles l3 and an extension plate 23 secured to the other pole. The other contact I5 is arranged between the arm l8 and the coil and is carried by a resilient blade 2| secured at one end to a fixed block 22. With this arrangement, the flux from the magnet tends to mov the block of magnetic material and draws the contact l4 into engagement with the contact I 5. 'In the attracted position of the said block IS a small air gap is left between it andsaidextension 23 and adjacent pole-piece l3 so that-when the magnet is deenergised the contact 14 may be retracted by a light biasing spring 24 connected between the arm l8 and an anchorage member 25. The main armature 10 rotates with the unwinding of the clock and is provided with an extension piece 26 shaped to engage the end of the arm l8" when the clock is nearly unwound so as tO-move the contact l4 into engagement with the contact [5 against the bias of the spring 24. The main rotary armature is also provided with a second extension piece 21 arranged to engage an arm 28 on which the contact [6 of the second pair or contacts is mounted, the other end of said arm being secured to an insulating block 29. The engagement of the second extension piece 21 with the arm 28 is arranged to take place when the main armature is reaching the end of its travel under the influence of the electromagnet.

In operation, when the electromagnet is deenergised, the main armature I is moved with the unwinding clock spring 30 until the first extension piece 26 closes the aforesaid contacts l4, I5. The electromagnet is thus energised and the small block of magnetic material I!) is attracted thereby ensuring that the contacts remain closed when the first extension piece and armature reverse their movement under the influence of the electromagnet. The main armature in being attracted by the electromagnet, stores up energy in a winding spring 3| which when the electromagnet is again de-energised drives the clock through the ratchet mechanism 35 and the shaft 32, at the same time stressing the maintaining spring 30 which keeps the clock running while the main spring is being restressed. Towards the end of the movement of the armature under the influence of the electromagnet, the second extension piece 2'! opens the biassed closed contacts l6, IT and interrupts the circuit. The biassed open contacts are thus allowed to open and the main armature moves in the reverse direction under the influence of. the spring 3! as indicated above.

It will be seen that the premature opening of the contacts l4 and 15 cannot occur as they are held closed by the flux between the extension plate 23 and one of the pole-pieces l3. Furthermore, the contacts l6 and H, which interrupt the circuit are only opened when the main armature has acquired an appreciable amount of kinetic energy, so that rapid opening is effected.

The arm 28 which carries the contacts 16 may be in the form of a bi-metallic strip which is encircled by a heating coil 33 in circuit with the electromagnet.

It will thus be seen that if the main armature fails to move sufliciently to open these latter contacts, due for example, to a fall in supply voltage, then the contacts will eventually open due to the heating of the bi-metallic strip and interrupt the circuit.

The construction shown in Figure 2 difiers from that described above in the means whereby the rotating armature closes the contacts [4 and 55 when the clockis run down. In this instance, instead of the lower end of the armature being provided with the upward extension 26, the upper end of the armature is provided with a contactmaking pin 33 which is arranged to be brought into engagement with a contact plate 34 secured to the arm l8 to which the contact I4 is secured. Thus, as in the previous construction, at the extremity of the movement of the armature it) during the running down of the clock, the two contacts l4 and R are brought together, energising the electromagnet coil H which then maintains the contact M in engagement with the contact l5 under the action of the block IQ of magnetic material. The armature is then moved under the action of the electromagnet until the extension piece engages the arm 28 and opens the contacts 16 and I! and breaks the circuit.

We claim:

1. .An electrically wound clock comprising a spring-energised clockwork mechanism, a switch, means for biasing the switch towards an open position, means operated by the running down of the clockwork mechanism to close said switch, an electromagnet energised by the closing of said switch, an armature adapted to be moved by the electromagnet so as to restress the spring of the clockwork mechanism and means influ enced by the electromagnet to maintain the switch closed during the resulting movement of said armature to restress said spring, a second switch in series with said first switch, means for biasing said second switch to closed position, and means operable by said armature toward the end of the spring restressing movement to open said second switch.

2. An electrically wound clock comprising a spring-energised clockwork mechanism, a switch, means for biasing the switch towards an open position, means operated by the running down of the clockwork mechanism to close said switch, an electromagnet energised by the closing of said switch, an armature adapted to be moved by the electromagnet so as to restress the spring of the clockwork mechanism, and a second armature influenced by the electromagnet and adapted to maintain the switch closed during the movement of the first armature in restress-- ing said spring, a second switch in series with said first switch, means for biasing said second switch to closed position, and means operable by said armature toward the end of the spring restressing movement to open said second switch.

3. An electrically wound clock comprising a spring-energised clockwork mechanism, an electromagnet, two switches in series with said electromagnet and a source of electric supply, an armature adapted to be moved by the electromagnet to re-energise the spring of the clockwork mechanism, meansior biasing one of said switches towards an open position, a second armature associated with that switch and adapted to be influenced by said electromagnet so as to maintain that switch closed during the movement of the first said armature in restressing the clock spring, means biasing the other switch to a closed position, means operated by the first said armature so as to open that switch when the armature has completed its restressing movement under the influence of the magnet, and means operated by the running down of the clockwork mechanism to close the first said switch.

4. An electrically wound clock comprising spring-energised clockwork mechanism, a switch, means for biasing theswitch towards an open position, means operated by the running down of the clockwork mechanism to close said switch, an electromagnet energised by the closing of said switch, an armature adapted to be moved by the electromagnet so as to restress the spring of the clockwork mechanism, means influenced by the electromagnet to maintain the switch closed during the resulting movement of said arma-. ture, and, a thermostatically controlled switch adapted to be influenced by heat generated in the electric circuit, and adapted to open the energising circuit when excessive heat is developed, said second switch being normally biased to .closed position, and means operable by said armature toward the end of the spring restressing movement to open said second switch.

5. An electrically wound clock comprising a spring-energised clockwork mechanism, a switch, means for biasing the switch towards an open position, means operated by the running down of the clockwork mechanism to close said switch, an electromagnet energised by the closing of with the electromagnet, which bimetallic strip is adapted to open the said second switch when current flows through said coil and electromagnet for a period of time substantially in excess of that required to move said first armature to a position in which the spring is restressed, and means operable by said armature toward the end of the spring restressing movement to open said second switch.

VICTOR JAMES SAMUEL RUSSELL. ERIC BEECROFT MOSS. 

